PHP调用WebService接口，谁给看下这段代码是什么意思呢？

$document=$proxy->document;echo <<<SoapDocument<?xml version=”1.0″ encoding=”GB2312″?><SOAP-ENV:Envelope SOAP-ENV:encodingStyle=”http://schemas.xmlsoap.org/soap/encoding/” xmlns:SOAP-ENV=”http://schemas.xmlsoap.org/soap/envelope/” xmlns:xsd=”http://www.w3.org/2001/XMLSchema” xmlns:xsi=”http://www.w3.org/2001/XMLSchema-instance” xmlns:SOAP-ENC=”http://schemas.xmlsoap.org/soap/encoding/” xmlns:si=”http://soapinterop.org/xsd“><SOAP-ENV:Body>$document</SOAP-ENV:Body></SOAP-ENV:Envelope>SoapDocument;

<?php<??>?>